Combustor End Cap Premixer Tubes Staged Fueling
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Solution Overview
Problem
Current combustor designs face challenges in preventing flashback and flame holding at high combustion gas temperatures, which can lead to damage, and in reducing NOx production, while also managing emissions and operational efficiency across varying conditions.
Innovation Solution
The combustor employs a plurality of premixer tubes arranged in an end cap with multiple fuel circuits supplied through axial and radial conduits, allowing for staged fueling and enhanced mixing of working fluid and fuel, thereby preventing flashback and reducing NOx production across a wide range of operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If higher combustion gas temperatures are used to improve thermodynamic efficiency, then thermodynamic efficiency is improved, but flashback or flame holding conditions occur causing severe damage to nozzles and increased NOx production
Solution Approach 1:
The combustor is divided into multiple zones with different fuel-air mixing characteristics. Premixer tubes create a first combustion zone with controlled mixing, while annular passages provide a second zone, allowing temperature and mixing control in different regions to prevent flashback while maintaining high overall efficiency
Solution Approach 2:
Different regions of the combustor have different local characteristics - the premixer tubes provide intensive mixing in their vicinity while annular passages provide less intensive mixing in other regions. This local differentiation allows high temperatures in some zones without causing flashback in others
2Use of energy by moving object
If higher combustion gas temperatures are used to improve thermodynamic efficiency, then thermodynamic efficiency is improved, but nitrogen oxides production increases due to increased disassociation rate of diatomic nitrogen
Solution Approach 1:
The combustion process is segmented into multiple zones with different residence times and temperature profiles. The premixer tubes create a first zone with rapid combustion and shorter residence time at high temperatures, while annular passages provide a second zone with different characteristics, thereby reducing overall NOx formation despite high combustion temperatures
Solution Approach 2:
The combustor maintains continuous combustion across multiple zones and operating conditions. The staged fueling system ensures continuous adjustment of fuel-air mixing to maintain efficient combustion while controlling temperatures and residence times to minimize NOx production across the full operating range
3Reliability
If lower combustion gas temperatures are used to reduce nitrogen oxides production and prevent flashback, then flashback prevention is improved, but carbon monoxide and unburned hydrocarbons production increases due to reduced chemical reaction rates
Solution Approach 1:
Combustion is divided into multiple zones where the premixer tubes create a first zone with intensive mixing and higher local temperatures that ensure complete combustion and reduce CO and unburned hydrocarbon formation, while annular passages provide a second zone with less intensive mixing and lower temperatures that prevent flashback and NOx formation
Solution Approach 2:
Different local mixing intensities are provided in different regions - the premixer tube region has intensive mixing for complete combustion, while annular passage regions have less intensive mixing with lower temperatures, allowing each region to optimize for its specific function
4Reliability
If a plurality of premixer tubes are used to enhance mixing and reduce hot streaks, then flashback prevention and NOx reduction are improved, but device complexity increases requiring improved fuel supply systems for staged fueling
Solution Approach 1:
The fuel supply system is segmented into multiple independent circuits - axial fuel conduits and radial fuel conduits - each supplying different premixer tubes. This segmentation allows staged fueling control while keeping each individual conduit relatively simple in design
Solution Approach 2:
The fuel supply system uses universal components (conduits, manifolds, control valves) that serve multiple functions - axial conduits supply fuel to multiple premixer tubes, radial conduits provide alternative fuel paths, and the system as a whole provides both cooling and combustion functions across different operating conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enables the combustor to operate effectively over a wide range of conditions without exceeding design margins related to flashback, flame holding, and emissions, improving thermodynamic efficiency and reducing harmful emissions.
Implementation Method 1
The premixer tubes enhance mixing between the working fluid and fuel to reduce hot streaks
Implementation Method 2
ignite fuel to produce combustion gases having a high temperature and pressure
Data Source
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AI summary
A combustor (10) includes an end cap (20) having upstream (28) and downstream (30) surfaces and a cap shield (32) surrounding the upstream and downstream surfaces (38, 30). First and second sets of premixer tubes (62, 66) extend from the upstream surface (28) through the downstream surface (30). A first fuel conduit (44) supplies fuel to the first set of premixer tubes (62). A casing (12) circumferentially surrounds the cap shield (32) to define an annular passage (26), and a second fuel conduit (46) supplies fuel through the annular passage (26) to the second set of premixer tubes (66). A method for supplying fuel to a combustor (10) includes flowing a working fluid through first and second sets of premixer tubes (62, 66), flowing a first fuel into the first set of premixer tubes (62), and flowing a second fuel through an annular passage (26) surrounding the end cap and into the second set of premixer tubes (66).